They replace the lost ions by active uptake through active transport
of ions from the surrounding waters. This is exhibited in freshwater fishes that
actively take in these ions through the gills. Most of the ions involved in osmoregulation in freshwater are those of Na+ and Cl-.
The oil extracted through these methods is referred to as "green crude" and it's not ready to be used as fuel until it undergoes another process called transesterification. This step adds more substances to the mix, including alcohol and a chemical catalyst that causes the alcohol to react with the oil. This reaction creates a mix of biodiesel and glycerol. The final step in processing separates the glycerol from the mixture and leaves a biodiesel that's ready to be used as fuel. Maybe one day it really will be easy being green.
You can read more about it here https://auto.howstuffworks.com/fuel-efficiency/biofuels/convert-algae-to-biofuel.htm
The biosphere. This is the layer that contains all life on the planet.
To be an agronomist, you should have an interest in science and a bachelor's degree. In college take agriculture, biology, chemistry, mathematics, physics, and statistics courses, as well as broad based general education courses, including English and speech. Hope this helps your question.